cool idle.....

[Charolais]

</font><font color="blue" class="small">( Is there any particular reason to idle a diesel that may have been running at 2000-2300 rpm for a couple of hours? )</font>

First I know nothing about the newer higher rpm compact diesels. And rpm's has little to do with the need to cool down.

If you're doing(example) deep tillage work and you have the engine under a load of about all it can handle without lugging, then the engine needs to cool down some before it's shut off.That's just one example. "The reason it needs to cool is so the valves won't warp." With farming on the decline most (not all) tractors are never loaded for long periods of time now. I just a few days ago wrote a reply about not having enough load in the first 50 hrs. to seat the rings on my FT. Once hay season started loading the tractor is no problem. When I hook that 90" CCM tiller to it the load is there also. /forums/images/graemlins/cool.gif

When I subsoil, pull a MOCO, round baler and that tiller for hours on end ,I always give the engine time to cool down when I'm finished. And on either of the tractors I have I can see the temp. needle going down while it's at a lower RPM. I don't go to idle for the cool down. I run 1,000 rpm's to cool. Reason being on older tractors the oil pumps sometimes get weaker. I want to keep enough rpm's on the engine to keep the oil flowing well while it's cooling also.

So my answer is yes it needs to cool if it's HOT from a load.

 

[woodchuckie]

L2800 & L3400 calls for a 5 minute warmup for engine oil and minimum 10 minute warm up for hydraulic fluid.



Stopping the engine: "After slowing the engine to idle, turn the key to OFF. Remove the key.

 

[cp1969]

</font><font color="blue" class="small">(
All the UPS trucks in our area are gas. Only the over the road trucks are diesel. All delivery are gas at least in our area. Gas is a whole different subject.

murph )</font>

Around here, they're diesel.

Why is gas a whole different subject?

 

[HGM]

To add a little more info, a diesel engine will run cooler at idle than at higher RPM. The reason for this is that there is an extremely low load condition at idle. This produces very little heat in the combustion chamber. Because a diesel has unlimited airflow, it tends to cool itself from the inside.. This may not be reflected in the coolant temp too quickly though.

 

[Charolais]

I guess it's possible it isn't necessary on todays tractors. I do remember in the 70's a MF dealer and a IH mechanic telling me to cool the engine down after a hard days work. I just got in a habit of doing it. It doesn't take long. When I see the temp. needle start down, I give it maybe 5 min. Most of the time my cool down takes place driving back down the highway. I do remember a post on a farm site telling about an Oliver tractor having warped valves and it was stated that it came from shutting the engine off while it was HOT.

 

[thcri]

</font><font color="blue" class="small">( </font><font color="blueclass=small">(
All the UPS trucks in our area are gas. Only the over the road trucks are diesel. All delivery are gas at least in our area. Gas is a whole different subject.

murph )</font>

Around here, they're diesel.

Why is gas a whole different subject? )</font>


The original question was pertaining to a diesel engine. And some manufactures do say on a diesel to cool down. I have never seen a manufacture say a gas engine needs to cool down.


murph

 

[HGM]

I would say that the gas engines produce as much heat at idle as they do under a load. Its always working against the throttle plate, creating a load in itself.

 

[demote]

My manual does say to let it idle prior to shutdown. I don't have it handy at the moment but it also states that after working, to taper the rpm down rather than instantly.

 

[cp1969]

</font><font color="blue" class="small">( The original question was pertaining to a diesel engine. And some manufactures do say on a diesel to cool down. I have never seen a manufacture say a gas engine needs to cool down.
)</font>

Nor have I, but I've never seen any manual for a turbocharged gasser, either.

What would cause a diesel to be more prone than a gas engine to ill effects from shutting down too early? I would be more inclined to give a five-minute idle a D-19 gas Allis Chalmers tractor after using it to plow than I would to idle a Kubota that's been pulling a wagon.

Since cooling off is the issue, I don't think the rules are governed soley by the fuel being burned.

 

[HGM]

</font><font color="blue" class="small">( I would say that the gas engines produce as much heat at idle as they do under a load. Its always working against the throttle plate, c <font color="blue"> </font> reating a load in itself. )</font>

Didnt this make sense????

 

[Highbeam]

I think I would disagree since at load, the amount of gasoline being burned is large and the efficiency roughly the same (actually a bit better) as at idle so the power being produced is much higher and therefor the waste heat load to the engine higher. I see the gas engine in my pickup heat up on a hill and not at idle. If the engine is 40% efficient then 60% of whatever fuel you are burning is going right into the coolant systems and out the exhaust.

True, at idle a gas engine is sucking against the throttle plate. But the amount of fuel required to do that isn't much at such a low rpm. Some of the older ford diesels had a flapper in the exhaust that would close to allow warm up at idle. That flapper could be modified to make it also serve as an exhaust brake!

 

[HGM]

Good points.I still tend to believe the gas burner might be warmer at idle than its diesel counterpart. My reasoning is simply because the diesel requires less energy to keep it running due to the lack of throttle plate, its a big air pump requiring little fuel, using mostly centrifical force of the flywheel and crank. Who truly knows? I've never actually measured it..../forums/images/graemlins/grin.gif

As for the PowerStroke Exhaust Backpressure Valve, yes I've seen it too. Seen it cause alot of pedistal failures because of high RPM oil pressures being diverted into the valve that is designed to be operated at idle only. /forums/images/graemlins/blush.gif

 

[cp1969]

</font><font color="blue" class="small">(

Didnt this make sense???? )</font>

No.

Highbeam's response illustrates what is wrong with your reasoning. Pulling against a throttle plate doesn't take all that much power--I figure it would take about 5.2 horsepower to spin a 350 ci engine at 800 rpm against a perfectly sealed intake.

 

[SkyPup]

Typically spark ignition gasoline engine combustion chamber temperatures are higher than diesels by about 400-500*F, including the piston crown and exhaust valves.

Don't worry about it unless you are operating under a heavy load for an extended period of time or you accidentally forgot to fill your radiator. /forums/images/graemlins/blush.gif

 

[SkyPup]

Diesels also have a difficult time reaching the minimum exhaust temperature to even reach the minimum temperature required to operate the catalytic converter, whereas gasoline engines do not experience that problem sine their exhaust gases at idle are so much hotter.